Process for preparing mercaptans



l w. l.. WALSH PRocEss FOR PREPARING MERCAPTANS Fild June e, 1957 2,925,443` PROCESS Fon PREPARING MERcAPrANs William L. Walsh, Glenrshw, Pa.,"assignor to Gulf Research & Development Company,`Pittsburgh, Pa., 4a corporation of Delaware l Application June 6, 1951,'ser'i'al No. $164,087 s Claims. (c1. 2604-609) This invention relates tothe preparation of primary and/or secondary mercaptans by the reaction of oletins and hydrogen sulde in the presence of a catalyst. f More particularly the'invention relates to they preparation of mercaptans by the reaction ofolefins with hydrogen suliide in the presence of specific catalysts and undercarefully controlled conditions.

Several methods of preparing mercaptans have been disclosed in the literature. The lirst reported synthesis involved contacting sodium ethyl sulfate with an aqueous solution of sodium hydrosulfde.` Other alkylating agents such as alkyly halides will react similarly. Mercaptaus can also be prepared by thecleavage of disuldes with metallic sodium or the treatment of Grignard reagents with sulfur. If hydrogen sulfide is added to propylene, isopropyl mercaptan is the 'product normally obtained as would be expected in accordance with Markownikoifs rule. Primary and secondary mercaptans, however, are not normally recovered in the last-mentioned procedure. Processes which direct the addition of hydrogen sulfide to olefins on the double bond carbon atoms contrary to Markownikolfs rule are of commercial interest because the products are primary mercaptans. These mercaptans are useful in preparing'synthesized thioester typeV synthetic lubricants and have other petrochemical applications'. 'j

I have found that substantial amounts of 'primary i 2,925,443 ,Ptit-safe@ Feb-1&3v 1260 Y Y' 2 o fins which can be used include lpropylene, butylene, pentene, hexene, octene-l, diisobutylene, pentadecylene, eicosene, etc. Y. L t The yield of mercaptanis improved if the iron chlo# ride is anhydrous and is present in the amount of maxif mum' solubility in the olefin. Thus a mixture of about onetenth percent to about ve percent by weight of iron chloride based. onthe v'olefin is satisfactory. `A ve percentA mixture Yis preferred in, the preparation from and/or secondary mercaptans can be obtainedV by a process which comprises reacting an olefin with hydrogen sulde in the presence of an organic peroxide and an iron chloride catalyst. Hydrogen sulfide gmust be present in the liquid phase and iniexcess during vthe reaction and it is absolutely necessary that the catalyst ernployed with the organic peroxide be iron chloride. The addition of the hydrogen sulfide to the olefin under the conditions of the present invention takes place contrary to Markownikofis rule.

A preferred method of carrying out the process in acoctene-l, for example, since thisY assures saturation of the olefin with the chloride. l t ,The ordinary olen which isrexposed to .air4 during storage contains peroxide formed autogenously.and,of

course, these peroxides areA suitable catalysts for the addifVV tion reaction.V However, since the f-amount vof peroxide formed may not be sufficient, some peroxides havevto be introduced to the 'reaction mixture to' insure therproper catalystk concentration. Y Y The peroxide catalyst must be present or satisfactory yields of mercaptans are not recovered. Best results'are obtained when the concentration of peroxide `is at least about ve-tenths percent-by volumeV of theoleiin feed, but no higher than about eightY percent by volume based on the olefin feed, since amounts in excess thereof merely increased the yield of disulfide without improving the yieldof the mercaptan. Examples of suitable peroxides are the peroxides of unsaturated organic compounds, such vas the peroxidesof ethers,l ketones, aldehydes, .for example, methylether peroxide, methylethyl ketone peroxide, acetoneperoxide, acetaldehyde peroxide,

etc. for the aromatic' peroxides,l for example, benzoyl peroxide, 'terpe'ne'peroxide tet'raline peroxide, 'cumene hydroperoxide,` diisopropylbenzene hydroperoxide, paramethane hydroperoxide, etc. T heV preferred peroxide for low temperature operation is methylethyl ketone peroxide; for highpressure reactions the preferred peroxide is cu'rnene hydroperoxide. Sufficient peroxide should be added to givel a resulting concentration of ,about ivctenths percent to about eight Ypercent peroxide by volume to the olefin feed, preferably about two to about ,four percent of the olefin feed. l v- The reaction takes place in the liquid phase and the hydrogen sulfide must be kept in the liquid phase in order to keep it present in excess` in the reaction mixture. This may be merely to assure that the yield of mercaptan will predominate over the yield of disulfide asta result of operation of the law lof mass action. ,It is more probable, however, that the excesshydro'gen sullide'acts asa solvent for the mercaptanl formed and withdraws it from contact with'the olefin; A molecular excess of n about `250y to 400 percent over the stoichiometric amount cordance with my kinvention is shown in Fig. 1, which is hereby included in the specification.

As shown in the drawing, in the flrstvstep anhydrous ferricv chloride or ferrous chloride 1 is'added to 'the olefin feed 2 and a precipitate is formed. Theisolution Y obtained which comprises the olefin4 and' an iron chlorideolen complex, is separated from the precipitate. Liquid hydrogen sulfide 4y and a suitable organic peroxide 5 are added to a cooled or pressurized reaction vessel 3.

The ferric chlorideolein solution is .advantageously added incrementallyv to the sulfide-peroxide mixture in order to obtain the desired results in accordance with this process.

The olefin feed 'can be anyolen, preferably y*one having a. terminal unsaturated carbon atom,.orja .mixture of these oleins. 'Ihus olens containing about three to about fifty carbon atoms in the molecule, for example,

. pentene, octene-l, diisobutylene, decene,-docene, pentadecylene, tetracontene, etc. are satisfactory feeds.. The preferred feed is an oleiin with about tive `to vabout twenty carbon atoms in the molecule. Examples of 01erequired forr the reactionis satisfactory.y A molecular excess of 300, percent over kthe stoichiometric amountv required for the reactionis preferred for aroom .tema

perature high pressure operation andan excess of 350 percent over thestoichiometric amount for the reaction run below the normal boiling point of hydrogen sulde. The pressure depends upon whether the reaction is carried out at a temperature below the normal boiling point of hydrogen sulfide or at room temperature.V If the reaction is carried out below the normal boiling point of hydrogen sulfide satisfactory pressures wouldbe fromabout 700 millimeters of mercury to abouttwo atmospheres, preferably about one atmosphere.` A suitable temperature range in this case would be from about C. to about -70 C. Ifthe reaction is carried out Iunder pressure, the pressure must be sucient to liquefy the hydrogen sulfide, a satisfactory pressure being about 250 pounds perV square inch gauge to aboutv450 pounds per square inchv gauge preferably aboutAQQ4 pounds per square inch gauge. Temperature'from about 20 to .40 C. in this case would be satisfactory, preferably about 25 C. Temperatures above 40 C. are rdinarilynot"desirablein'cases where Vthey might have an adverse effect on the equilibrium between the mercaptan, the olefin, and hydrogen sulfide The optirriuni"'yield of mercaptan is recovered if sufficient iron Vchloride Vc'atalyst'is added to saturate the olefin with the chloride. Since concentrated solutions of the chloride inthe olen can be easily prepared, the olefin and iron chloride catalyst are conveniently added together. This addition can be accomplished by the addition preferably in incremental amounts Vof about onehalf percent of the total,at`one minute intervals over a period of about one-half hour when the reaction is run at a temperature below the boiling point of hydrogen sulfide. If the reaction is lrun' under pressure, the mixture can be added in increments of about tive percent of the total at ten minute intervals' over a period of one hour. Thev solution of iron chloride in olefin may be added to the pressurized vessel by forcing the liquid into thevessel with nitrogen under higher pressures.

"In the second step of the low temperature reaction, the mixture is stirred for an additional half hour and the peroxide still present is advantageously, though not necessarily destroyed in any convenient manner as some reaction with the peroxide apparently can take place to a small extentduring the warming up of the mercaptan product mixture from T6O C. to room temperature, which leads to the production of disulfides since the hydrogen sulfide evaporates and leaves an excess of olefins. The peroxide can be destroyed when the reaction is carried out at low temperature, by the addition as shown by reference numeral 6, of any reducing agent such as any amine having two to six carbon atoms in the molecule, for example,propylarnine, propylene diamine,'nbutyl amine, tertiary amylamine, p-amylamine, n-hexylamine, etc., preferably propylene diamine. The lamine is added to give 'an amine concentration of about one-tenth to five percentin the solution, preferably about five-tenths percent.

" In the last` step the separation of the mercaptan from the by-products is completed by any conventional means ati?, as 4for exampleby distillation of the reaction mixtureat a temperature of about 199 C. and apressure of about one atmosphere, or chromatography on alumina using isopentane as an eluent 'can be used to effect the Separation# The procedure described hereinabove is representative of one possible process under the invention and therefore I have no intention of limiting 'the invention thereto.

The following examples further illustrate specific embodiments of the invention.

Example 1 A charge of 200.0 grams of methylal was placed in a one` liter three-necked flask equipped with a stirrer, Dry Ice condenser, thermometer, and dropping funnel. The ask was placed in a Dry Ice-acetone bath, which cooled the methylal to Y 70 C., four mols of hydrogen sulfide and four grams of a 60 percent solution of methylethyl ketone vperoxide in dimethyl phthalate were added to the methylal at this temperature. The chloride catalyst (3 grams of anhydrous ferrie chloride) was added to 112 grams of octene-l anda precipitate was obtained in a solution comprising the olefin and an iron-chloride-olefin complex. The precipitate was removed and the solution added dropwise in one milliliter increments to the methylal-hydrogensullide mixture over a period of about onehalf hour. The reaction mixture was stirred for an additional half hour and ten grams of propylene-diamine was added to the solution to destroy any'remaining' peroxides'. The reaction mixture was allowed to warm to room temperatu're and the methylal removed by distillation.v The lremaining liquid was fractionated and the products recovered.: A 60 percent yield of primary octyl mercaptan and "six percent normal diotnyl Y'sulfide Vwas recovered.

4 This yield is based on the 1-olefm content of the octane-l charged; Approximately 28 percent of the octene-l was recovered unreacted.

These data illustrate a typical low temperature reaction. A substantial yield of primary mercaptan results when the reaction is carried out under these conditions. Y

' Example 2 The effect of solvent on the mercaptanV yield and on the distribution of mercaptan and disulfidein the product was investigated; i

The reaction was run under conditions identical to the conditions used in Example l, Vexcept that thereaction was carried out in the absence of the methylal solvent. A yield of 51 percent primary octyl mercaptan and five percent normal dioctyl sulfide was recovered.

Comparison of these data with the data in Example l indicates that 'a slight improvement in the yield of mercaptan and ratio of mercaptan to disulfide in the product canV beexpected if the reaction is carried out in the presence of rnethylal, acetal, ethylal, etc. as solvents.

Example 3 Diethylether was evaluated as a solvent and its effect on the mercaptan yield and distribution of mercaptan Example 4 The effect of concentration of ferrie chloride was investigated by preparing a saturated solution of anhydrous ferrie chloride in octene-l and using this solution .as a feed Stoch The methylal solvent (200 grams) was placed in a one liter three-necked ask equipped with a stirrer, Dry Ice condenser, thermometer yand dropping funnel and cooled to 70 C. in a Dry-Ice-acetone bath. A charge of four mols of hydrogen sulfide and vfour grams of 60 percent solution Vof methylethyl ketone in dimethyl phthalate was added to the flask, A saturated solution of anhydrous ferrie` chloride in octene-l was prepared by adding 24 grams of anhydrous ferrie chloride to 120 grams Yof' octene-l, stirring the mixture and filtering to remove Vthe undissolved ferrie chloride. This solution was placedin an addition tube and added to the peroxide hydrogensulfide solution. The addition was made in one milliliter increments over a period of one-half hour. The reaction mixture was 4stirred for an additional half hour and lten grams of propylenediamine was added to the solution to destroy any remaining peroxides. The reaction mixture was then allowed to Warm to 25 C., the methylal was removed by distillation and the remaining liquid fractionated A yield of 66 rpercent primary octyl mercaptan was recovered. The yield of normal dioctyl sulfide was four percent.

An improvement in the yield off normal octyl mercaptan and in the ratio of mercaptan to disulfide in the product isnoted if themaxium amountof ferrie chloride soluble in octene-l is added as a catalyst.

These data demonstrate that an improved lyield results when ferrie chloride is added up rto the'saturation point of 'the fsre Chloride in the olefin- Example 5 @seitige 9i Peroxide..

` chloride-oleiin complex.

l charge of 200 grams of"methylal `w`a`s placed in'a one liter three-necked ask equipped with a stirrer,Y Dry Ice Condenser, thermometer, and dropping funnel. The ask was placed in a Dry Ice-acetone bath which cooled the methylal tok -70 C., four mols of hydrogen ksulfide was passed into the methylalat -70'C. The chloride catalyst (3 grams of anhydrous ferrie chloride) was' added to 112 grams of octenel and a precipitate was obtained in a solution comprising the olelin and an iron The precipitate was removed and the solution added dropwise in one milliliter increments to the methylal-hydrogen suliide mixture overa period of about one-half hour. The reaction mixture was stirred for an additional half hour and allowed to warm to room temperature. The methylal was removed by distillation'and the remaining liquid fractionated. A yield of only one percent normal octyl mercaptan was recovered. A large part (95 percent) of the octene-l was recovered unreacted. l

It is apparent from the above that no appreciable addition of hydrogen sulde to olefin Vtakes place unless the peroxide catalyst is present.

Example 6 The elect of increasing the quantity of kperoxide catalyst on the yield of mercaptan was evaluated.Y Acharge of 20() grams of methylal was placed in a one .liter threenecked ask equipped with a stirrer, Dry Ice condenser, thermometer and dropping funnel. The ask was placed in a Dry Ice-acetone bath which cooled the vrnetl'lylalto -70 C. A charge of four mols of liquidhydrogen sulfide was added to the methylal at this temperature, 16 grams of a 60 percent solution of methylethyl ketone peroxide in a dimethyl phthalate was added. The chloride catalyst (3 grams of anhydrous ferrie chloride) was added to 112 grams of octene-l and a precipitate was obtained in a solution comprising the olefin and an iron chloride-olefin complex. The precipitate was removed and the solution added dropwiserin one milliliter increments to the methylal-hydrogen sulde mixture over a period of about one-half hour. The reaction mixture was stirred for an additional halfl hour and 10 grams of [propylenediamine was added to the solution to destroy any remaining peroxides. The reaction mixture was then allowed to warm to room temperature. The methylal was removed by Vdistillation and the remaining liquidv fractionated. A yield of 56 percent primary octyl mercaptan and one and one-half percent normal dioctyl sulde was recovered.

No apparent improvement resulted from the fourfold increase in the amount of peroxide added, although possibly an improvement in the ratio of mercaptan to disulde resulted. Y

The data presented in Examples and demonstrate that no appreciable reaction takes placeunless .the organic peroxide is present and indicates that the'addition of peroxide in excess of the ratio of about 2. grams of peroxider per mol of hydrogen sulde has no apparent benelicial eiect on the mercaptan yield.

Example 7 i Several 4runs were completed in 4which diierent cata- 6 octene-l and a precipitate. lwasobtained in a solution comprising the olefin and an aluminum chloride olen complex. The precipitate was removed andthe solution added dropwise, in one mol milliliter increments to the methylal-hydrogen sullde solution overa period of about one-half hour. The reaction mixturewas stirred for an additional half hour and ten grams of propylenediamine Was added to the solution to destroy any remaining peroxides. The reaction mixture was lallowed to warm to room temperature and the methylal removed by distillation. The remaining liquid was fractionatedand the products recovered. vAyield of only one andthree-tenths percent normal octyl mercaptan was recovered. No effort was made to determine the yield of disulfide since 80 percent of the octene-l was recovered unreacted.

It is apparent from this data that anhydrous aluminumV chloride does not electively catalyze the addition of hydrogen sullde to olefins under these conditions.

Example 8 was substituted for anhydrous ironchloride in an eiort .to find another suitable catalyst.

A charge of 200 grams of methylal was placed in one liter Vthree-necked flaskrequipped with a stirrer, Dry Ice condenser, thermometer, and dropping funnel. VThe flask was placed in a Dry Ice-acetone bath, which cooledthe methylal to -70 C., and four mols of hydrogen sulfide andV fourgrams of methylethyl ketone peroxide in dimethyl phthalate was added to the methylal at this ternperature. The chloride catalyst, three grams of anhydrous magnesium chloride, was dissolved in 112 grams of octene-l and this solution added dropwisein one milliliter increments, Yto the methylal-hydrogen sulde solution over a period rof about one-half hour. yThe reaction mixture was stirred for an additional half hour and -ten grams of propylenediamine was' added to the solution to destroy any remaining peroxides. The reaction mixture was. lallowed lto warm: to room vtemperature andthe methylal removed by distillation. The remaining liquid was fractionated and the products recovered. The yield of mercaptan was less than Vone percent and ninety-one percent of the octene-l was recovered unreacted.'

It is apparent from the above that magnesium chloride is not a satisfactory catalyst` Vfor the reaction and that iron chloride is necessary under the conditions outlined,

Example 9 four grams of a percent solution of methylethyl ketone lysts were substituted for anhydrous iron chloride. The

lresults were not satisfactory unless the catalyst was anhydrous iron chloride.

AIn the iirstfof theseruns a charge of 200 grams of methylal was placed in a one liter three-necked flask equipped ywith a stirrer,`Dry'Ice condenser,'thermome ter, andV dropping funnel. The ask was placed in a Dry Ice-acetone bath, which cooled the methylalto -'70 C four mols of hydrogensulde and four grams ofva 60T percent solution of Vrnethylethyl ketonevr peroxide in "dimethyl phthalate was addedr to the methylal at this temperature. The'chloride catalyst (3 grams-of anhydrs aluminum chloride)`was adddto 112i5giam`s of peroxide in dimethyl phthalate. The chloride catalyst (2 grams of anhydrous stannic chloride) was addedto 112 grams of octene-l and a precipitate was obtained in a solution comprising'the olen and a stannic chlorideolen complex. The precipitate was removed and the solution added dropwise to the hydrogen sulfide-peroxide solution, incrementally over a period ofV one-half hour. The reaction mixture was stirred for anadditional half hour and ten grams of propylenediamine-was added to the solution to destroy any remaining peroxide. The reaction mixture was allowed to warm to room temperaiture, the liquid fractionated and products removed. A

yield of two percent mercaptan and one percent disuliide.

More than one-half (53 percent) of was recovered.

octene-l was recoveredunreacted.

A comparison of this yield with the yield obtained when anhydrous ferrie chloride was used under the same conditions (Example 2) indicates anhydrous stannic chlorideis not a satisfactoryA catalyst for the v;react'.icin'.^

Example I Anhydrous magnesium chloride was substituted for ferricchloride to determine whether it would be an effective catalyst in a reaction where no solvent was present. A one liter three-necked flask equipped with stirrer, Dry Ice condenser, thermometer, and dropping funnel was cooled in a Dry Ice-acetone bath to 70 C., and four mols of hydrogen sulfide was added to the flask along with four grams of a 60 percent solution of methylethyl ketone peroxide in dimethylphthalate. The chloride catalyst (2 grams of anhydrous magnesium chloride) was added to 112 grams of octene-1 and a precipitate was obtained in a solution comprising the oleiin and a magnesium chloride-olelin complex. The precipitate was removed and the solution added dropwise in one milliliter increments to the hydrogen sulfide-peroxide solution over a period of about one-half hour. The reaction mixture was stirred for an additional half hour and ten grams of propylenediamine was addedto the solution to destroy any remaining peroxides. The reaction mixture was allowed to warm to room temperature, the liquid fractionated and the product recovered.

No appreciable yield of normal octyl mercaptan or disulfide was recovered from this reaction. Essentially all (9.7 percent) of the octene-l was recovered unreacted.

A comparison of this yield with the yield obtained when anhydrous ferric chloride was used as the catalyst under the same conditions (Example 2) shows anhydrous magnesium chloride is not a satisfactory catalyst for the reaction.

An examination of the data presented in Example 7 through Example 11 emphasizes the importance of an anhydrous iron chloride catalyst. None of the other chlorides effectively catalyzethe addition of hydrogen sullide to the olelin on the carbon atom to which the greatest number of hydrogen atoms is attached in contraq position to Markownikols rule.

Example 11 The effect of water of crystallization on the catalytic power of the iron chloride was investigated.

A charge of 100 grams of methylal was placed in a one liter three-necked flask equipped with a stirrer, Dry Ice condenser, thermometer, and dropping funnel. The ask was placed in a Dry Ice-acetone bath, which cooled the methylal to 70 C., four mols of hydrogen sulfide and four grams of a 60 percent solution of methylethyl ketone peroxide in dimethyl phthalate were added to the methylal at this temperature. The chloride catalyst (3 grams of FeCl3.6H2O) was added to 112 grams of octene-l and a precipitate was obtained in a solution comprising the olefin and an iron chloride-clelia complex. The precipitate was removed and the solution added dropwise, in one milliliter increments, to the methylal-hydrogen sullide solution over a period of about one-half hour. The reaction mixture was stirred for an additional half hour and ten grams of propylenediamine was added to the solution to destroy any remaining peroxides. The reaction mixture was allowed to warm to room temperature and the methylal removed by distillation. The remaining liquid was fractionated and the products recovered. A yield of 27 percent primary octyl mercaptan and eight percent normal dioctyl disulfide was recovered. More than one-half (52 percent) of the octene-l was recovered unreacted.

The deleterious effect of water of hydration is shown by the decrease in yield of mercaptan and the unfavorable elect on the mercaptan-sulde ratio in the product.

Example 12 The efr'ect of the physical state of the hydrogen suliidel on the yield was evaluated in a run at room temperature. Octene-l (112 grams) was placed in a one liter, three-necked liask equippedv with stirrer, thermometer., diossine funnel. and sas. islet tubo- A Charge ot "four grams of a 60 percent solution of methylethyl ketone peroxide in dimethyl phthalate and three grams of anhydrous torrie chloride were added to the octoneel.. A stream of hydrogen sulfide was passedV through the solution for a period o-f two hours while the octene-lwas stirred vigorously. Only a trace of vprimary octyl rnercaptan was recovered. These data indicate that the hydrogen sulfide must be present in the liquid state for the reaction to proceed satisfactorily.

The further effect of the physical state of the hydrogen suliide on the yield is shown below in Example 13.

Example 13 A charge of 112 grams of octene-l was placed in a one liter three-necked liask equipped with a stirrer, condenser, thermometer and inlet tube for hydrogen sullide. The liask was placed in a Dry Ice-acetone bath which was maintained at a temperature of 53 to 55 C. The octene-l was treated Vwith 3 grams of anhydrous ferrie chloride at ro-om temperature before being placed in the ask. The reaction mixture was cooled to 53 C. andV then two grams of a V60 percent solution of methylethyl ketone peroxide in dimethyl phthalate was introduced therein. Hydrogen sulde was passed through the reaction mixture at the rate of 2 mols per hour for one hour at a `temperature of 53 to 55 C. At this temperature, of course, no liquid hydrogen sulde is present, since the boiling point is 59.6 C. at atmospheric pressure. One gram of n-butyl amine was addedk Example 14 Low temperature processes present several operational and economic difficulties, hence the possibility of using high pressure to keep the hydrogen sulfide present in the liquid state was investigated.

A 1000 milliliter Magna Dash Autoclave, stirred by a stirrer paddle moved up and down by a magnetic tension spring mechanism was charged with grams of hydrogen sulde. The pressure in theautoclave rose to 250 pounds per square inch gauge. A four gram charge of a 60 percent solution of methylethyl ketone peroxide in dibutyl phthalate was added to the autoclave by using nitrogen pressure to overcome the pressure of lthe liquid hydrogen sullide. The olefin ferric chloride catalyst charge stock was prepared by adding three grams of anhydrous ferrie chloride to 112 grams of octene-l. A precipitate was obtained in a solution comprising the olefin and an iron chloride-olelin complex. The precipitate was removed and the solution was passed into the `autoclave in approximately live percent increments at ten minute intervals by using nitrogen pressure to overcome the internal pressure in the autoclave. pressure in the autoclave was approximately 40() pounds per square inch gauge when all the charge had been added. The temperature remained at 25 Yto 35 C. throughout the addition. The reaction mixtureiwas stirred under these conditions for approximately 16 hours. The unreacted hydrogen sulfide was removed by slowly decreasing the pressure to atmospheric, andy the liquid product fractionated. The yield of primary octyl mercaptan was 17 percent and the yield of normal dioctyl suliide live percent based on the l-olefin content of the octene-.L Approximately 70Vpercent of the osterie-1 was recovered unreacted.

it is apparent from these data that an appreciable yield of primary octyl mercaptan can be recovered if the reaction is run at room temperature and under sufficient pressure to keep the hydrogen sulfide present as a liquid.V

The

Y in a Dryr Ice-acetone Example 1K5 Example 16 Y I'he effect of placing both` the peroxide catalyst and the ferrie chloride co-catalyst in the octene-l was studied.

Methylal (200 grams) was charged to a one liter threenecked flask equipped with a stirrer, Dry Ice condenser, thermometer, and dropping funnel. The fiask was placed in a Dry Ice-acetone bath, which cooled the methylal to 70 C., and four mols of hydrogen sulfide was added to the methylal at this temperature. The chloride catalyst (3 grams of anhydrous ferrie chloride) was yadded to 112 grams of octene-l and a precipitatey was obtained in a solution comprising the olefin and an iron chloride-olefin complex. This precipitate was removed and four grams of a 6,0 percent solution of methylethyl ketone peroxide in` dimethyl phthalate was added. This octene-l solution was added dropwiseV in one milliliter increments to the methylal-hydrogen sulfide mixture over a period of about one-half hour and the reaction mixture was stirred for an additional half hour. The reaction mixture was allowed to warm to room temperature, the methylol removed by distillation, the remainingliquid fractionated and the products recovered. `A 43 percent yield of primary octyl mercaptan and a greater than ten percent yield of normal dioctyl sulfide was recovered. Approximately 17.5 percent of the octene-l was recovered unreacted.

Example 17 In this run diisobutylene was substituted for the octene- 1 as the olefin charge material. Four mols of hydrogen sulfide was charged to a one liter three-necked fiask equipped with a stirrer, Dry Ice condenser, thermom eter, and dropping funnel. The ask had been placed bath,y which cooled the hydrogen sulfide to 70 C. Four grams of a 60 percent solution of methylethyl ketone peroxide in dimethyl phthalate was added to the hydrogen sulfide solution. The chloride catalyst (3 grams of anhydrous ferrie chloride) was dissolved in 112 grams of ldiisobutyleneand this solution added dropwise in one mllliliter increments to the liquid v hydrogen sulfide over a period of about one-half hour. The reaction mixture was stirred for an additional half hour. The reaction mixture was allowed to warm up to room temperature, the remaining liquid fractionated vand the products recovered. A 25 percent yield of primary and secondary octyl mercaptan was recovered. Ap-

10y proximately 62 percent of the diisobutylene was covered unreacted. p

This experiment shows that other olens behave ras octene-l does in this reaction' Octene-l was used as the olefin feed in most of these examples as it is readily'available in the laboratory. Any of the other types of oleflns mentioned in the specification can be substituted for octene-l in commercial production and similar results obtained.

The purity of the primary octyl mercaptan prepared was ascertained by preparing the 2,4-dinitrochloroben-V zene derivative and comparing the melting point with the known value. In all cases asubstantially pure product was recovered from'the distillation.

These examples are purely illustrative of preferred embodiments of the invention and I have no intention to limit the invention thereby. l A

Obviously many modiiications and variations of the invention as hereinbefore set forth may be made without departing from the essence and scope thereof and only such limitations should be applied as are indicated in the appendedV claims.

kI clairnz f '1. A process for the preparation of a mercaptan which comprises adding anhydrous iron chloride to an olefin and thereafterreacti'ng said olen with hydrogen sulfide Y `by incrementally adding the solution of iron chloride and olelin to excess liquid hydrogen sulfide Vand an organic peroxide.

2. A process for the preparation of a mercaptan Iwhich comprises adding anhydrous iron chloride to an olefin and thereafter reacting said olefin with hydrogen sulfide by incrementally adding the solution of iron chloride and olefin-to excess liquid hydrogen sulfide and methylethyl ketone peroxide.

y 3. A process for the preparation of a mercaptan which comprises adding anhydrous iron chloride to an olefin and thereafter reacting said olefin with hydrogen sulfide by incrementally adding the ,solution ofV iron chloride and oleiin to excess liquid hydrogen rsulfide and cumene hydroperoxide. Y

4. A process for the preparation of a mercaptan which comprises adding anhydrous iron chloride to octenc-l and thereafter reacting said octene-l with hydrogen sulfide' by incrementally adding Ythe solution of iron chloride and octene-l to excess liquid hydrogen sulfide and an organic peroxide.

5. A process for the preparation of a mercaptan which comprises adding anhydrous iron chloride to octene-l and thereafter Vreacting said octene-l with hydrogen sulfide by incrementally adding the solution of iron chloride and'octene-l to yexcess liquid hydrogen sulfide and methylethyl ketone peroxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,052,268 Williams et al. Aug. 25, 1936A 2,352,435 Hoeffelman-et al. June 27, 1944 2,443,852 Eaton ct al. June 22, 1948 2,531,602 Bell NOV. 28, 1950 

1. A PROCESS FOR THE PREPARATION OF A MERCAPTAN WHICH COMPRISES ADDING ANHYDROUS IRON CHLORIDE TO AN OLEFIN AND THEREAFTER REACTING SAID OLEFIN WITH HYDROGEN SULFIDE BY INCREMENTALLY ADDING THE SOLUTION OF IRON CHLORIDE AND 